How to create child theme of already active and customized theme

I just started at a new company with multiple WordPress sites and none of them use child themes.

I've seen posts here about using comparison scripts to compare the files to a fresh version of that theme, but I'm not too familiar with scripting and no one even provided an example of how to do that.

I'm also wondering how I would go about getting all of the other settings inside WordPress to carry over (theme customizations, homepage settings, etc.). I know on some themes there can be a lot of drag-and-drop type editing that you lose when moving to a new theme. I already made that mistake once here and had to quickly change it back to the parent theme.

TL;DR
How can I create child themes and keep everything looking the same as parent themes that are already active?

I just started at a new company with multiple WordPress sites and none of them use child themes.

I've seen posts here about using comparison scripts to compare the files to a fresh version of that theme, but I'm not too familiar with scripting and no one even provided an example of how to do that.

I'm also wondering how I would go about getting all of the other settings inside WordPress to carry over (theme customizations, homepage settings, etc.). I know on some themes there can be a lot of drag-and-drop type editing that you lose when moving to a new theme. I already made that mistake once here and had to quickly change it back to the parent theme.

TL;DR
How can I create child themes and keep everything looking the same as parent themes that are already active?

• themes
• child-theme

Share Improve this question asked Jan 4, 2019 at 13:31 ManlyManly 14366 bronze badges 2

• 2 There's no general answer. It depends entirely on what the original theme is. You should ask your theme author. – Jacob Peattie Commented Jan 4, 2019 at 13:39
• @JacobPeattie I was afraid of that. They're all different themes haha – Manly Commented Jan 4, 2019 at 13:50

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This is tough. I don't know of an automated way of doing this because every theme is different and who knows what changes you (or whoever) have already made to the original theme.

In my opinion, if you want to do this correctly and with the best results you are going to need to do this manually.

I would, setup a local install of wordpress, download the original unedited theme and install it on my local setup, then make your child theme. You could go through the theme options in the admin fairly easy just by opening your local site and the live site side by side and comparing. This will get all your settings aligned. You could also grab any styles from the customizer and put in your local site.

With the site settings aligned, now you need to make the same edits to your files but this time within your new child theme. Depending on what IDE or text editor you use, you can probably install a diff tool that will compare the differences between files. Similar to this online diff tool.

If you go slow and go section by section or page by page and compare the live version with your local install eventually you will have a matching child theme.

Not fast but it will get you there!